Today, rapid typing keyboard technologies typically embody three primary attributes that are viewed as necessary or desirable for an effective implementation—low actuation force, significant travel distance, and tactile “snapover”.
With regard to a low actuation force, studies have found that in order for a user to rapidly type, it is desirable to provide an overall key top actuation force from around between 40-80 grams. Having a light actuation force permits easy actuation and reduces fatigue.
With regard to travel distance, in order to rapidly type, many current technologies provide an overall travel distance (i.e. the vertical distance a key travels) from between 2-4 millimeters. In technologies that implement keyboards using elastomeric domes that are collapsible under pressure for key actuation, the travel distance is required because of the physical and mechanical nature of the domes that are employed. Specifically, the physical structure of the dome requires a longer travel distance in order to allow the dome geometry to adequately collapse, thus providing a response with tactile characteristics that are necessary or desirable for rapid typing. In addition, this travel distance is important because as a key top moves relative to a finger, frictional forces of this relative movement provide an additional tactile element (i.e. localized skin stretching) that plays an important role in a user's recognition of an electronic switch closure. The travel distances required by current dome technology significantly limit the form factor, e.g. the thickness of an associated keyboard. That is, keyboard thickness is significantly limited by the use of dome technology. This, in turn, reduces keyboard construction potentials and the various environments in which such keyboards can be used.
With regard to the tactile snapover, such is an important aspect for rapid typing. A snapover, as will be appreciated by the skilled artisan, creates a specific tactile response which is desirable in typing scenarios, particularly those that are rapid typing scenarios. The notion of snapover refers to a relationship between force and travel and is defined as a specific area on a standard keyboard force displacement curve. Snapover is what users typically associate with a valid electronic switch closure. In addition, this association between the tactile response and an electronic switch closure allows the user to learn to not rely solely on visual confirmation during typing, such as looking at the screen between each typed letter, to ensure that they are typing correctly. In current rubber dome technologies, this snapover is achieved due to the collapsing of the rubber dome. Typically, force exerted on the key and hence, on the rubber dome increases until the dome collapses and achieves switch closure. Due to the geometry and the physical characteristics of the rubber dome, achieving a snapover effect requires a sufficient amount of force and travel to reach the snapover point.
Against the backdrop, a need remains for keyboards that provide adequate user feedback and address the three attributes mentioned above.